There are several different IEEE standards for configuring wireless networks and devices. For example, IEEE standards that have been popularized include 802.11, 802.11a, 802.11b, 802.11g, 802.11h, and 802.11n, 802.16, and 802.20, which are hereby incorporated by reference in their entirety. According to these standards, wireless network devices may be operated in either an infrastructure mode or an ad-hoc mode.
In the infrastructure mode, the wireless network devices or client stations communicate with each other through an access point (AP). Referring now to FIG. 1, a wireless network 10 that operates in the infrastructure mode includes an AP and at least one client station that communicates with the AP. The first wireless network 10 includes one or more client stations 12-1, 12-2, . . . , and 12-N (collectively referred to as client stations 12) and one or more APs 14. The client stations 12 and the AP 14 transmit and receive wireless signals 16 over an RF channel. The AP 14 may be connected to a distributed communications system 18 such as the Internet using a router 20 and/or a modem 22, although many other types of network connections are possible.
Referring now to FIG. 2, an exemplary AP 14 for a WLAN device includes a media access control (MAC) device 24, a baseband processor (BBP) 26, a radio frequency (RF) transceiver 28, and a crystal oscillator (XOSC) 30. The AP 14 may include a system on chip (SOC) 32 that includes the MAC device 24, the BBP 26, and other SOC components 34. For example, the other SOC components 34 may include a host interface 36, a processor 38, and memory 40. Typically, the RF transceiver 28 and the XOSC 30 are located external to the SOC 32. In another implementation, an amplifier portion of the XOSC 30 is integrated with the SOC 32 and a crystal portion of the XOSC 30 is located external to the SOC 32. In another implementation, the RF transceiver is integrated with the SOC 32.
The RF transceiver 28 wirelessly transmits/receives data to/from client stations in the wireless LAN. The RF transceiver 28 includes a phase-locked loop (PLL) 42 that receives a reference signal from the XOSC 30. The PLL 42 generates a clock signal based on the reference signal from the XOSC 30. The RF transceiver 28 includes a transmitter 44 and a receiver 46.
The BBP 26 modulates/demodulates signals between the RF transceiver 28 and the MAC device 24. The BBP 26 includes an analog to digital converter (ADC) 50, a digital to analog converter (DAC) 52, a demodulator 54, and a modulator 56. The ADC 50 receives signals from the receiver 46. The ADC 50 communicates with the demodulator 54, which demodulates the signals. A MAC interface 58 communicates with the MAC device 24. Conversely, the MAC device 24 sends signals to the MAC interface 58. The modulator 56 modulates the signals from the MAC device 24 and the DAC 52 outputs signals to the transmitter 44.
An AP in a wireless network transmits a beacon at a target beacon transmission time (TBTT). The TBTT time functions in conjunction with a timing synchronization function (TSF) timer to synchronize the AP and the client stations in the wireless network. The AP and all of the client stations in the wireless network include a TSF timer.
Referring now to FIG. 3, the AP periodically transmits an exemplary beacon frame 60 at a TBTT. The beacon frame 60 includes a TSF time 61 and a beacon interval 62. The TSF time 61 is a time according to the AP's TSF timer when the beacon frame 60 is sent. The beacon interval 62 is a time between each TBTT. The client stations receive the beacon frame 62 and operate according to the information contained therein. Each client station updates its own TSF timer according to the TSF time 61. Further, the beacon interval 62 indicates future TBTTs to the client stations. In this manner, the AP maintains synchronization in the wireless network.
In some types of networks, all of the client stations need to transmit data regularly, for example, at each beacon interval. One example of this type of network is a wireless console gaming application operating in an infrastructure mode.
Referring now to FIG. 4, a wireless gaming network 64 includes a host gaming device 66 and one or more client gaming devices 68. The client gaming devices 68 include wireless local area network (WLAN) hardware and operate as client stations in an infrastructure mode network. The host gaming device 66 also includes wireless LAN hardware and operates as an access point (AP) in the wireless gaming network. The wireless gaming network allows for greater mobility of the client gaming devices 68. Those skilled in the art can appreciate that the host gaming device 66 and the client gaming devices 68 may be a game console or any other suitable implementation of an AP and one or more wireless client stations. The host gaming device 66 synchronizes wireless communication with and between the client gaming devices 68 as described above in FIG. 3.
Further, the host gaming device 66 (and the AP 14 as described in FIGS. 1 and 2) and/or the client gaming devices 68 communicate on a particular RF channel. Although multiple RF channels may be available, a wireless network typically uses a single RF channel for transmitting and receiving data. Typically, the host gaming device 66 and/or the client gaming devices 68 transmit and receive data on an RF channel in the 2.4 gigahertz (GHz) band or the 5 GHz band.